4 Flute End Mill
Total found: 325
Four flutes is the standard geometry for steel, stainless, cast iron and heat-treated alloys. The reason is not that four edges cut more than two - it is that four shallow flutes leave a much larger core, and the core is what resists bending and torsion. A 4-flute cutter holds its position in the cut, and holding position is what produces a size you can measure and a finish you can accept.
The range below covers 4-flute cutters in square, corner radius and ball nose profiles across the diameters we stock, coated and uncoated. Details are on each product page.
This is the part most flute-count advice leaves out, and it decides whether a cut chatters.
How far a tooth is engaged depends on radial width. At 25% radial engagement the arc of contact is about 60 degrees. A 4-flute cutter has 90 degrees between teeth. So at 25% radial there are moments when no tooth is cutting at all, then a tooth slams in - and that on-off loading is exactly what excites chatter.
Two ways out. Raise radial engagement to around half the diameter, where the arc reaches 90 degrees and one tooth is always in the cut. Or, if the strategy requires light radial engagement, go up in flute count - five flutes close the gap to 72 degrees, and high-flute-count tools exist for exactly this reason.
A cut that sings at 20% radial and runs quietly at 45% is not a tool problem.
The instinct with a light radial pass is to back the feed off. That is backwards, and it destroys tools.
When radial width is less than half the diameter, the tooth never reaches full chip thickness - it skims. At 10% radial engagement the actual chip is only about 60% of the programmed feed per tooth, so to cut a proper chip you have to feed roughly 1.7 times more, not less.
Feed too little and the edge stops cutting and starts rubbing. Rubbing generates heat without a chip to carry it away, and in stainless it work-hardens the surface ahead of the tool so the next pass is cutting something harder than the material you started with. Most 4-flute tools that die early in stainless died of this.
Four is the default. Five is worth it when the cut is light radially and the flute count is what keeps a tooth engaged, or when the job is finishing and the extra edge tightens the cusp pattern.
Five costs chip room, so it belongs in steel and stainless where chips are short, not anywhere the swarf has to travel.
Slotting aluminum. At full width the chip has nowhere to go, and four flutes do not give it room. Use 2 flutes, or three on an adaptive path.
Deep pockets in soft material. Same reason - the chip has to travel the whole flute length to get out, and packing it is what breaks the tool.
Plunging. The chip has to come straight back out of the hole being formed, which needs volume rather than edges.
Diameter follows the feature and the internal corners it has to produce - 1/8", 3/16", 1/4", 3/8" and 1/2".
Coating matters more here than on any other flute count, because these tools work where it is hot. AlCrN and AlTiN are built to keep hardness at temperature and are the reason a coated tool survives a cut that strips an uncoated one.
Profile: corner radius unless the drawing forbids it. Four flutes will not save a sharp corner - the corner is still the first part of the tool to fail, and a radius is what postpones it.
Prices and stock are on every product page and you can order online without waiting for a quote. Delivery is free across Alberta and we ship anywhere in Canada.
We run our own machine shop in Calgary and cut with these tools ourselves. If a 4-flute cutter is chattering or dying early in stainless, send us the radial engagement, the feed per tooth and the material - it is nearly always one of those two numbers rather than the tool.
